In 1958, a retired materials handling engineer in Pittsburgh, Pa., U.S.A., named Herbert H. Hall, prepared a technical paper for the American Society of Mechanical Engineers describing a modular series of large freight containers which could move in global interchange. The object was to achieve greater efficiencies and economies in transport by being able to have the shipper select that size of container which best suited his cargo and still enjoy the benefits of interchangeability with the sizes in the same series. Mr. Hall's paper was introduced into ISO/TC 104 (document 104 N 2) upon initiation of the ISO project in 1961. It was his thinking that proved to be the guiding light for the Technical Committee's work. It was his logic that ultimately emerged to become the foundation for the present ISO International Standards in this field.
The early work of TC 104 called for careful analysis of the operational environment within which the containers would move. Calculations had to be made, and confirmed by test, of all the accelerations and decelerations that might be encountered in typical intercontinental container operations. From these data came the basic requirements for the construction of the Standard Containers. The fact that containers in service have borne up so well structurally is a testimonial to the thoroughness and accuracy of the Committee's early work.
In the abstract, TC 104 identified for all containers, eight points in space, prescribing their exact coordinates and thereby defining the dimensions and tolerances of the "outer envelope" of the container sizes. These were to locate the corner fittings of every container regardless of type. Next the Committee specified what external forces would have to be sustained by the container at these points. Gravitational loads caused, for example, by stacking containers on one another, or inertial loads caused, for example, by the pitching and rolling of a ship, all had to be established. Then internal loads had to be defined, such as those introduced by the cargo bearing against the inside walls of the container. Test methods were also created that reflected the routine service conditions encountered in normal operations, making allowances for the fluctuations that were likely to occur.
Out of this approach came a container system that permitted dimensional and functional interchangeability among all of the container types. If at some future time a unique type of container might be required and developed, the application of the basic guidelines for the Standard Container will assure compatibility with the existing ISO handling and transport environment.
Inbound cargo shipping containers (sometimes called containerized cargo or freight containers) are conventionally unloaded from container ships by cranes and transported by container carrying vehicles to a dockside container storage yard. The same cranes and vehicles are used to transport outbound containers from the container yard and load them onto container ships for export.
If the container yard is large relative to the number of containers which must be stored then the containers are laid on the ground in rows. If the container yard is small relative to the number of containers which must be stored (as is typically the case) then the containers are stacked atop one another to conserve valuable space.
A freight container is not simply a large steel box with a flat bottom which may be placed, for example, on a conveyor belt and moved along like a huge pallet. In fact, a freight container can only be lifted by or stored on its corner castings, which are relatively very small, 6.5 ins..times.6 ins. (164.5 mm.times.149.0 mm). Apart from these four small corner fitting castings, the bottom of a container typically consists of a number of fairly light gauge crossbeams about one foot (30 cm) apart which sustain a wooden floor. The crossbeams are typically attached to the floor angle or bottom of the side plating and neither they, nor the floor angle, touch the supporting surface when the container is in storage.
When ISO freight (cargo) containers (hereafter termed "containers") are stacked one upon another, they must be vertically aligned so that the weight of the upper container(s) is transmitted vertically downwards from the corner castings of the upper container to the upper corner castings of the container below and thence, via the strong (in compression) corner posts, directly to the bottom corner castings of the lowest container. Containers normally have sufficient strength to sustain no more than four other loaded containers above them (subject to the weight in each individual container), provided always that the stack is properly placed with each container's bottom corner castings standing directly upon the upper corner castings of the container below.
A standard freight container has large doors at one end which significantly reduce the container's ability to withstand transverse racking forces which would be imposed upon it if one side were to be raised above the other.
Containers stored in the storage yard are commonly shuffled from one location to another in a continuous effort to speed the loading and unloading of container ships. For example, a group of containers may be moved to clear an area in the yard to receive an inbound shipload of containers. The inbound containers can be unloaded and moved into the cleared common storage area more quickly than would be the case if each inbound container had to be moved into a random storage location in the yard. Similarly, a group of outbound containers may be moved into a pre-cleared yard storage area in preparation for loading the entire group of outbound containers onto a ship which is about to arrive, or which is being unloaded. The outbound containers can be loaded onto the ship from a common storage area more quickly than would be the case if each outbound container had to be moved to the ship from a random storage location in the yard. Similarly, containers may be moved so as to gain access to a particular inbound container for which road or rail transport has arrived.
The continuous shuffling and lifting of stored containers causes a number of problems. Although records are usually kept of the yard location in which each newly arriving container is stored, those records are often not updated to reflect every shuffling movement of each container. For example, if an outbound container is stacked beneath two other containers which are not outbound, then those two must be lifted off the outbound container and moved to another storage location before the outbound container can be moved. The other two containers are not normally moved back into the stack location from which they were moved. Moreover, the operator who moves them may not note their new location(s) in the yard's records. Even though those two containers may be moved only a short distance, confusion can result when they have to be located for loading or for transport to an outbound ship, especially if they are repeatedly moved in a series of unrelated shuffling operations. Valuable time is wasted while "lost" containers are located.
The ability to manage container placement and movements is also adversely affected by the inability to precisely locate and track the movement of individual containers within the yard. Even if a container's location is known, repeated shuffling operations may have "buried" that container beneath and/or behind many other containers, all of which must be moved (i.e. shuffled) to gain access to the desired container. Repeated container shuffling also increases the potential for damaging the containers.
Computerized systems have been developed to automate the process of locating and tracking individual containers stored within a container yard. However, because such systems typically rely on human driven vehicles to move containers, they require human operator input to indicate that containers have been shuffled into different locations. Such systems are therefore subject to the same problems that are outlined above if the vehicle operator fails to input information respecting each and every container movement. In a busy container yard, with many simultaneous container movements continually ongoing, it is impractical to record each and every container movement. Even if the location of every container in the yard is known, and even if every container movement is tracked to reflect the new location of every shuffled container, significant time is still required for conventional container handling equipment to shuffle the containers about the yard and transport them to and from container ships.
The following two patents disclose cargo moving and storage systems.
Greub, U.S. Pat. No. 4,887,953, provides a storage system of endless bucket belts P.sub.1, P.sub.2, P.sub.3, P.sub.4, etc. Each belt carries a plurality of shelves or gondolas R.sub.1, R.sub.2, R.sub.3, R.sub.4, etc. A control means operates motors M.sub.1, M.sub.2, M.sub.3, M.sub.4, etc. which actively drive the respective belts to bring selected shelves or gondolas into position adjacent a shelf serving apparatus 3 capable of loading the shelves/gondolas with containers or retrieving containers from the shelves/gondolas. Greub does not disclose apparatus which move only in response to displacement of a container off of or onto an elevator.
Lemelson, U.S. Pat. No. 3,750,804, teaches a warehousing system with storage racks and the location of a transport aisle between opposed ends of a rack. A stacker crane is located in the aisle. Conveyorized storage racks are also used.
The mechanisms and systems patented by Lemelson and Greub both involve endless belt conveyors for the lateral movement and some degree of tilting while transferring the stored object to and from the elevator. They make no provision whatsoever for the support of the containers by the corners only and, especially in the case of the device of Lemelson, make no provision for the large forces involved when moving cargo containers which can weigh up to 34 Metric tonnes each. Neither of the mechanisms disclosed could possibly handle or store freight containers.
Sarvary, U.S. Pat. No. 3,622,020, discloses a three-dimensional pallet-storage system wherein goods are stored in pallets at a plurality of different storage levels and in a plurality of rows of storage locations at each level. Pallets are removed from an area of bulk storage by means of a transfer trolley and conveyed to a pallet replenishment area. A picking tower is located adjacent a live store area and has associated therewith a two-directional transfer device capable of removing pallets from the live store, to a point adjacent a handler, transferring the pallet after unloading of the goods in a direction normal to the direction of removal and then moving the pallet in the opposite direction from the removal direction to insert the pallet in an empty row of the live store. The transfer trolley and two-directional transfer device both have at least one cross travel member to effect the transfer of the pallets from one storage location to another.
Hartbauer, U.S. Pat. No. 3,547,282, discloses an apparatus for and method of removably storing a plurality of boxlike containers each of which is adapted to receive therein a substantial number of articles such as cartons of facial tissue. The apparatus includes a storage bank adapted to have such boxes or containers inserted through the front face of the storage bank into one of a plurality of openings therein which are arranged in horizontal rows and vertical tiers, each of the boxes when inserted into the storage bank being automatically coupled in tandem orientation to a preceding box previously inserted into the same opening and at the same time being operative to displace such preceding box inwardly toward the rear of the storage bank. The apparatus further includes a box transporter mechanism having moving elements cooperating with elements provided by the box to pick up the boxes individually at a pickup station and then transport each such box to a desired location or opening along the storage bank and insert the box thereinto, the transporter mechanism also being used for subsequently removing boxes from the storage bank and for transporting the boxes to a discharge station. Upon such removal of a box from the storage bank, the box is automatically uncoupled from a preceding box immediately therebehind after the latter box has been advanced to a forward position adjacent the front face of the storage bank. The transporter mechanism includes an elevator cage movable vertically so as to handle boxes at different levels and it further includes a conveyor mechanism arranged with the elevator cage for vertical movement therewith, but also being movable horizontally with respect to the elevator cage for the purpose of picking up, discharging, and inserting boxes into and removing them from the storage bank.
U.S. Pat. No. 3,792,785, Weir, discloses an automated freight terminal wherein a plurality of stacker cranes transfer shipments between load-unload boom conveyors, shipment staging compartments, and an indexable distribution conveyor comprised of a series of interconnected carts. The stacker cranes are provided with elevators, and each elevator supports an endless belt conveyor that can be side-shifted toward selected carts of the distribution conveyor or toward staging compartments which components are also provided with endless belt conveyors. The conveyors on the carts or in the staging compartments are powered from the stacker crane conveyor, and shipments can be moved off the crane conveyor onto the conveyors of the compartments or cart, or vice versa. Incoming freight shipments are routed from a truck to a boom conveyor to a stacker crane, and the stacker crane transfers the shipments directly to the staging compartments or to the distribution conveyor for transfer to the operating area of another stacker crane. The distribution conveyor is indexed in predetermined distances to bring different sets of carts to the stacker cranes so that shipments can be routed anywhere in the terminal. Outgoing freight shipments are handled in a reverse manner.
U.S. Pat. No. 4,085,759, Seragnoli, discloses a system for connecting n cigarette manufacturing machines by a cigarette container feeding apparatus to the loading mechanism of the grouping hopper of a packeting machine. Each manufacturing machine has means for filling single successive containers. Empty containers are rhythmically supplied and removed, and full ones removed and supplied, by stepwise moving conveyor devices, with the aid of storage conveyor devices to compensate for output unbalances between the several machines. The speed of the packeting machine is substantially equal to the sum of the operating speed in the time unit of the n manufacturing machines and the speed of each of said n machines is equal to v/n. The system comprises, for each manufacturing machine, a transfer device group having a pair of transfer devices, for respectively transferring full and empty containers; a storage conveyor device for bidirectional intermittent movement; and a memory device connected to each manufacturing machine and to the packeting machine and arranged to control actuating means of each transfer device, once every n steps of the conveyors, to compensate for operating unbalances of the machines.
Neither of these systems disclose or relate to a facility for handling large heavy ISO containers.